Auto Parts: DOHC, pushrod engines, sohc engine

Question
What is DOHC(Dual overhead Camshaft)?
Please explain more about this.

Answer
Hi Aryan,

You've answered your own question. DOHC means Dual Over Head Cam. This is opposed to an OHV engine (Over Head Valves) and similar to a SOHC (Single Over Head Cam).

OK, what this means is that above the cylinder head on your engine there should be TWO camshafts instead of the typical, one camshaft. DOHC are typically used where there is three or more valves per cylinder as in a 16 valve in-line four cylinder engine. A SOHC engine of the same design would probably only have 8 valves, 4 for intake and 4 exhaust whereas the DOHC engine would probably have 8 intake and 8 exhaust valves, typically four per cylinder.

Are they better? Not really. An engine block that can accept both SOHC and DOHC heads would probably notice a small increase in power and torque using a DOHC instead of the SOHC but would surely notice an increase in fuel usage more with the DOHC than with the SOHC.

An OHV engine is one where the cam is integrated into the engine block and not the head and usually uses pushrods to actuate the over head valves. Pushrod engines can have 4 valves per cylinder also but not many of them because of the increased weakness of that many parts moving around at the same time which is why Over head cams were invented.

Thanks for the question, I hope this information was helpful to you.
Fred
Knucklebusters Used Auto & Truck Parts, Inc.
www.knucklebusters.us
570-453-0910
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